USING DEMULSIFIERS FOR PHASE BREAKING OF WATER/OIL EMULSION

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1 Petroleum & Coal ISSN Available online at Petroleum & Coal 55 (1) 26-30, 2013 USING DEMULSIFIERS FOR PHASE BREAKING OF WATER/OIL EMULSION Amir Mosayebi, Reza Abedini* Department of Petroleum Engineering, Mahallat Branch, Islamic Azad University, Mahallat, Iran, *Corresponding author (R.Abedini) Received October 1, 2012, Accepted January 30, 2013 Abstract Demulsification (emulsion breaking) is necessary in many practical applications as the petroleum industry and waste water treatment in environmental technology. The emulsion stability results from the presence of interfacial barrier preventing coalescence of the dispersed water droplets. The most effective method to overcome the problem is to demulsify the crude by using demulsifiers. The demulsifiers will destabilize the interfacial film between the droplets. Demulsifiers with amine and polymeric groups were used for breaking of water in crude oil emulsion, in this study. The relative rate of water separation were determined via breaker tests. The polymeric group demulsifier had better performance on breaking emulsion than amine group demulsifiers. Keywords: demulsifier; interfacial film; emulsion; droplet; stabilize. 1. Introduction Water-in-oil emulsion is formed during the production of crude oil, which is often accompanied with water. The stability of the emulsion is ranging from a few minutes to years depending on the nature of the crude oil and to some extent the nature of water [1].A recent report has suggested that an equivalent volume of water accompanied the daily production of some 60 million barrels of crude oil [2]. Under the production conditions, a proportion of this water can become intimately dispersed throughout the crude oil as small droplets. The natural petroleum emulsion resulting from the secondary production consists of crude oil as dispersion medium and brine as dispersed phase, normally stabilized by natural chemicals such as asphaltenes, resins, solid such as clays and waxes [1]. For asphaltenes in particular, the presence of heteroatoms in the essentially aromatic structure imparts amphiphilic characteristics [3]. Emulsions are undesirable because the volume of dispersed water occupies space in the processing equipment and pipelines, increased operating and capital costs. Moreover, the characteristics and physical properties of oil change significantly upon emulsification. The density of emulsion can increase from 800 kg/m3 for the original oil to 1030 kg/m 3 for the emulsion. The most significant change is observed in viscosity, which typically increases from a few mpa.s or less to about 1000 mpa.s [4]. Chemical methods are the most common method of emulsion resolution in both oil field and refinery. The application of chemicals designed to neutralize the effects of emulsifying agents have great advantages of being able to break an interfacial film effectively; without the addition of new equipments or modifications of the existing equipment. 2. Materials and Methods The crude oil applied as model in this study was obtained from the Refinery of Tehran. Specifications and some physical and chemical properties of this crude oil are listed in table 1. There are wide ranges of demulsifiers that can be used in demulsification of crude oil emulsions. From the literature study, the demulsifiers used in this paper are shown in Table 2. In this study, three demulsifiers, amine groups, polymeric and alcohol were used for water in crude oil emulsions demulsifications. A 500 ml gratuated cylindrical glass was used as sample container.

2 Table. 1 Specifications and properties of crude oil used as model. Character paraffinic API 37 Density (g.cm -3 ) Viscosity at 25 C,(cp) 12.6 Table. 2 Types of chemical demulsifiers used as model. No. Name HLB Concentration (mol.l-1) 1 EO/PO Block Copolymer Hexylamine Pentylamine Ethyleneglycol (EG) Sodium dodecyl sulfate (SDS) Water in crude oil emulsions were propared at room temperature with a mixer at speed 1200 rpm. First, distilled water was used as water phase (dispersed phase) and crude oil as oil phase (continuous phase). The emulsifiers used in this study for emulsion formulation were ethoxylated nonyl phenols. For different demulsifiers, water in crude oil emulsions were prepared and tested. The water separation in percent was calculated as separation efficiency from volume of water observed in the breaker as follows: V olumeiofiseparatediwater, iml % iwateriseparatedi ( ml / ml ) 100 originalivolumeiofiwateri in itheiemulsion, iml Tables 3 and 4 shows the effect of different demulsifiers on crude oil emulsion stability (% water and oil separation), respectively. Table. 3 The effect of different demulsifiers on crude oil emulsion stability (% water separation ml/ml). Time (min) EO/PO Block Copolymer A. Mosayebi, R. Abedini/Petroleum and Coal 55(1) 26-30, Hexyl amine Pentyl amine Ethylene glycol (EG) Sodium dodecyl sulfate

3 Table. 4 The effect of different demulsifiers on crude oil emulsion stability (% oil separation ml/ml). Time EO/PO Block Copolymer Hexyl amine Pentyl amine Ethylene glycol (EG) Sodium dodecyl sulfate Results and Discussion A. Mosayebi, R. Abedini/Petroleum and Coal 55(1) 26-30, Figure 1 and 2 show separation of water and oil from water in oil emulsions as a function of time, respectively. The process of chemical demulsification of a water in crude oil emulsion involves the acceleration of the coalescence as well as the film rupture process. Dispersed water droplets approach each other and flatten to form a thin film of continuous oil phase between them, the outward drainage flow of the film can create gradients in interfacial tension which then oppose and slow down such drainage [5]. The tendency for the drops to coalesce will be the van der Waals forces when the lamellae are thin enough, and the restoring forces will be the Gibbs- Marangoni effect (figure 3). This effect will operate due to the distortion and increase in surface area of the drops as they get close together. So, it can be concluded that the stability of emulsions is largely affected by the nature of the interfacial film and surfactant adsorption mechanisms [6]. As shown in figure 1, after 200 min, the amount of water separated from water in crude oil emulsion for EO/PO Block Copolymer, hexyle amine, pentyl amine, ethylene glycol and SDS were 7, 7, 2, 0 and 0 %, respectively. After 1000 min, there was no further water separation observed in the entire sample tested. After a long duration (2200 min), EO/PO Block Copolymer had separated water highest percentage (55 %), followed by hexyle amine (34 %), pentyl amine (29 %), ethylene glycol (22 %) and SDS (20 %), respectively. As shown in figure 2, it was found that the percentage of oil separation from water in crude oil emulsions were more than water separation in the entire sample tested. After a long duration (2200 min), EO/PO Block Copolymer had separated water highest percentage (57 %), followed by hexyle amine (35 %), pentyl amine (29 %), ethylene glycol (28 %) and SDS (23 %), respectively. SDS had Lowest percentage of water and oil separation in the entire sample tested. The effectiveness of emulsion breaking between the amine group demulsifiers and polymeric can be compared in terms of their ability in separating the water and oil from emulsions. Experimental results obtained in this study, it was founded that the polymeric demulsifiers were more effective in emulsion breaking than amine group demulsifiers.

4 A. Mosayebi, R. Abedini/Petroleum and Coal 55(1) 26-30, Fig. 1. The effect of different demulsifiers on crude oil emulsion stability (percentage of water separation) Fig. 2. The effect of different demulsifiers on crude oil emulsion stability (percentage of oil separation) 4. Conclusions Fig. 3. The Gibbs-Marangoni effect [7]. Crude oil in the reservoir is found together with formation water. The stable emulsion resulted from the stress caused from the flow of crude oil and formation water. Emulsions create a lot of problems such as corrosion. For these reasons, crude oils must be treated by using demulsifiers. Demulsifiers accelerate the emulsion breaking process. The demulsifier adsorbs at the interfacial film, weaker the interfacial barrier and separate the water droplets. The amine and polymeric group demulsifiers wrer used for breaking of water in crude oil emulsion. Polymeric group demulsifiers were more effective in emulsion breaking than amine group demulsifiers. Polymeric group demulsifier obtained 55 % water and 57 % oil, respectively.

5 References A. Mosayebi, R. Abedini/Petroleum and Coal 55(1) 26-30, [1] Bhardwaj, A. and Hartland, S.: (1998). Studies On Build Up of Interfacial Film At The Crude Oil/Water Interface. J. Dis. Sci. Tech., 19(4): [2] Ivanov I.B., and Kralchevcky, P.A. (1996). Stability of Emulsion Under Equilibrium and Dynamic Conditions. Coll. Surf. A. Physcochemical and Engineering Aspects. 128: [3] Sjoblom, J., Ming Yuan, L., Hoiland, H and Johansen, J.E. :(1990). Water-in-Crude Oil Emulsions from the Norwegian Continental Shelf, Part III. A Comparative Destabilization of Model Systems. Colloid and Surfaces. 46: [4] Fingas,M., Fieldhouse, B., Bobra, M., and Tennyson, E.: (1993). The Physics and Chemistry of Emulsions. Proceed Workshop on Emulsion. Marine Spill Response Corporation, Washington, DC. [5] Tambe, D.E. and Sharma, M.K.: (1993). Factor Controlling the Stability of Colloid- Stabilized Emulsions: I. An experimental investigation. J. Coll. Int. Sci. 157: [6] Myers, R. H. and Montrogomery, D.C.: (2002). Response Surface Methodology: Process and Product Optimization Using Designed Experiments. 2nd Edition. Canada:.John Wiley & Sons. [7] Porter, M.R.: (1994). Use of Surfactant Theory. Handbook of Surfactants. Blackie Academic & Professional. United Kingdom